Thallous compounds as rich mixture fuel additives



Aug. 7, 1951 THALLOUS COMPOUNDS AS RICH MIXTURE FUEL ADDITIVES Filed Nov. 5, 1947 M. R. BARUSCH ETAL m I w I 3.0 i- I A w w 2G A 1a r I to 1.0 o I n- S-I-TIMLLOUS NAPHTHEMTE E at 6 I20 I30 1 MO 17o PERFORMANCE NUMBER Ml ME N TORS $112M. M" @i /NQAQV 42 m aways Patented Aug. 7, 1951 UNITED STATES PATENT OFFICE THALLOUS COMPOUNDS AS RICH MIXTURE FUEL ADDITIVES Maurice R. Barusch, Richmond, and George H. ,Denison, Jr., San Rafael, Calif., assignors to California Research Corporation, San Francisco, Calii'., a corporation of Delaware Application November 3, 1947, Serial No. 783,838

4 Claims. (01.44-68) This invention relates 'to spark ignition engine fuels; more particularly, to spark ignition engine fuels boiling in the gasoline boiling range and having improved antikncck characteristics under 2 in supercharged engines using rich mixtures, as in aircraft take-oil and climbing. Under these latter conditions, many fuels that have been rated as 100 octane or better by the F-2 method and rich mixture conditions and to a method for pre-' th 3 -3 th d have proved to be inferior fuels paring such fuels. under conditions of extreme power requirements In an mp o r h a h e level f pv where the engine is supercharged and a rich fueloutput of a gasoline engi e before knocking 00- air mixture is used. Fuels are rated under rich curs, it has become the practice to supercharge mixture nditi n by t cFR-AFD-F4-443 t engine. w ver, p ha s s a means Method (hereinafter called the F-4 Method). of increasing the power output before oc This method is described in a report by the Cois li it d, n that a iv n fu l an t l rat just s ordinating Research Council dated April 20, 1943, uch uperc a ina eyo d which, excessive and entitled cr'a Supercharge Method of Test knoiiking u sy employing rich fuel-ail for Knock Characteristics of Aviation Fuels. mixtures, that is, a ratio of fuel to air greater i t th description of which has been than a required C p o us a widely circulated and which is widely used, rates t-er amount of Supe a c be tulera fuel under conditions of supercharging and rich oted. t a given fue than if a lean m ture i fuel-air mixtures, and it correlates well with full p oye ut t s e p e a has the limiscale ratings of fuels, as in aircraft take-off and tations, in that when -a certain richness is c1imbing The engine employed is a ingle 1 r h d. t e e m fi s and the power ou p der, liquid cooled, gasoline spark i nition engine; ps the cylinder is the same as that used in the F42 n n rt o in e the P w r output still method of rating fuels. Manifold fuel injection further before knocking occurred, numerous antiis employed; the engine i equipped for superknock h ve b d d 0 the base fuel charge; the compression ratio is 7:1, and the en- Amo'ng such antiknock agents have been metal gin is operated at1800 R. P. M., 375 F. jacket carbonyls o iron pentacurhbnyi) and temperature, 225 F. air temperature and ethyl lead. Such other agents as have been P spark advance BTC. Further details as to design p d f t e 111051? part, 1655 effective ha and operation can be attained from the above tetraethyl lead or are more expensive. Despite 30 ti d report, e advantages of a t y l s use is (115- Ratings by the F-4 method are given herein in advantageous owing-to several factors, such as its terms of t n number up to 100 octane and, t y n i nd y to po lead above 100 octane, they are given as performance pounds in carburetors, manifolds, valves, cylinnumbers and as equivalents of iso-octane plus ders or exhaust pip s n-milliliters of tetraethyl lead per gallon of fuel, A further method of trying to solve the problem n being a, positive number usually of the order of of knock s be n he ma a u f Special 1 to 1-0. For convenience hereinafter, F-4 ratings base els by cracking, y isomerization of will be referred to as so many octane units (e. g., straight to branched chain hydrocarbons and by 0 9 octane it where th fuel rated is not more alkylation of isoparafilns with olefins. Judicious blending of stocks so prepared with one another and/or with straight run distillates has also contributed to upgrading base fuels.

Even by combining the advantages of tetraethyl lead, superior base stocks, supercharging and rich mixtures, it is difficult to meet certain aviation power requirements, such as is necessary in take-off of heavily loaded aircraft. Also, the above noted disadvantages inherent in the use of tetraethyl lead remain.

Fuels-of the gasoline type have been rated heretofore generally by the CPR-ASTM-D357-43T Method and the CFR-ASTM-D614-43T Method. hereinafter designated as the F-2 method and the F3 method, respectively. These methods have rated fuels dependably for lean mixture use;

i. e., use under normal or cruising conditions, but they are not dependable for rating fuels for use than the equivalent of pure iso-octane (which has an octane number of and, where the fuel rated is more than the equivalent of pure isooctane, as so many performance numbers, and as S+n (e. g., S+l.0) where 8 stands for S-reference fuel, which is iso-octane (2,2,4-trimethyl pentane) and 11. for the number of milliliters of tetraethyl lead required to be added to iso-octane to produce a fuel having the same F-4 value as the fuel rated. (The number of milliliters of tetraethyl lead, 11. means n-milliliters of the compound Pb (CzHs) 4) l The performancenumber is used to designate the relative knock limited power output of fuels having octane numbers above 100 when tested according to the F4 procedure. Pure iso-octane has an octane number of 100 and a performance number of 100. A fuel having a performance ratings, without entirely relying upon the selection of base fuel and the use of large amounts of tetraethyl lead.

It is a further particular object of the invention to provide a gasoline type of fuel for aircraft engines which provides improved antiknock characteristics under conditions of supercharging and of rich fuel-air mixtures.

- It is a further object of this invention to pro-- vide unleaded aviation fuels having high antiknock and especially high 1 4 ratings. I

Other and further important objects of this invention may be noted from the specification and claims presented hereinbelow. 1 It has been discovered that organo thallium compounds in which the thallium is in a monoelectrovalent state improve the rich mixture antiknock ratings of spark ignition engine fuels. Thus, the rich mixture antiknock ratings of spark ignition engine fuels may be improved by an admixture therein of organo monoelectrovalent thallium compounds. The organo monoelectrovalent thallium compounds may be used in any hydrocarbon fuel boiling in the gasoline boiling range, that is, having an initial boiling point of about 100 F. and a final boiling point of about 400 F. (ASTM, D-86 distillation). "Preferably, however, a petroleum base fuel is employed which may be a synthetic petroleum (e. g., petroleum distillate from the Fischer-Tropsch process, etc.), straight run petroleum distillates, fuels prepared by thermal and/r catalytic cracking, an alkylate (e. g., sul furic acid or HF isoparaflin-olefin alkylate) aromatic fuels, olefinic fuels, naphthenic fuels and blends of two or more of the above and other types of fuels.

Until recently, it was the practice to evaluate fill are effective in improving the F-Z- ratings of spark ignition engine fuels when used at the concentrations noted hereinbelow. It does mean that the F-4 rating of a spark ignition engine fuel having an F-2 rating as low as 85 will be improved when that fuel is used in a spark ignition engine operating at rich fuel-air mixture.

The monoelectrovalent compounds of this invention may be represented by the following formula:

wherein M is the metal thallium in the monoelectrovalent state and x represents an organic anion. Examples of x anions are the following: the carboxyl anion of thallous carboxylates (e. g., thallous oleate, thallous stearate, thallous benaoate, thallous methyl benzoate, thallous phenyl acetate, thallous naphthenate, etc.), the alcoholate anion and phenate anion (R0-) of the thallous alcoholates and the thallous phenates (e. g., thallous ethylate, thallous cetylate, thallous phenate. thallous cresylate, etc.) and the amino anion (BN1?) (RR1N) ofthe thallous amides (e. g., thallous diethylamide, thallous dicetyl amide, thallous dicresyl amide and thallous diphenyl amide). In these formulas, R and R1 represent saturated and unsaturated aliphatic radicals, aromatic radicals, aralkyl radicals, alkaryl radicals or combinations ofthese radicals The R and R1 radicals may contain, as substituents, polar groups such as chlorine, bromine, hydroxyl, ether, keto, mercapto, etc. The R and R1 may or may not be the same.-

As noted hereinabove, the thallium cation of an organo thallium compound of this invention has a valence of one. When an organo thallium compound wherein the thallium has a valence of zero is added to a fuel as a rich-mixture additive, the F-4 rating of the blended fuel is less than that obtained when using a thallium compound wherein the thallium has a valence of one. For example,

- when 0.05% of thallium triethyl (wherein the valthe antiknock value of spark ignition engine fuels I under lean mixture conditions only. However,

as noted hereinabove, it has become necessary to develop fuels having high rich mixture antiknock values; i. e., high F-4 ratings. Previous methods used for increasing the rich mixture antiknock values of base fuels having octane numbers above 100'have not been desirable economically because of the great amounts of required additive. However, it is a peculiarity of monoelectrovalent thallium compounds (1. e., thallous compounds) that only small amounts are necessary for increasing the F-4 octane ratings (1. e., the performance numbers) when the base fuels have a minimum F-4 octane number of 100 (i. e., a performance number of 100). Although the monoelectrovalent thallium compounds are especially effective for improving the rich mixture ratings (the F-4 rating) of base fuels having minimum F4 octane ratings of 100, the monoelectrovalent thal lium compounds are also effective when added to base fuels having F-2 octane number ratings as low as 85; i. e., lean mixture octane number ratings as low as 85. However. this does not means ence of thallium is zero) was added to an S-reference base fuel having an octane number of 100, the F-4 rating of the blended fuel was equivalent to that of the S-reference fuel plus 1.0 ml. of TEL per gallon of fuel. However, when 0.05% of thallium naphthenate (wherein the valence of thallium is one) was added to an S-reference base fuel having an octane number of 100, the F-4 rating of the blended fuel was equivalent to that of the S-reference fuel plus 2.8 ml. of TEL per gallon of fuel. These results are contrary to expectations. gano compound wherein the metal was in a zero valence state was more eflective as a rich-mixture additive than was a metal organo compound wherein the same metal was in a valence state of +1, +2, etc. For example, when 0.05% of tetraethyl lead (wherein the valence of lead is zero) was added to an S-reference fuel having an cetane number of 100, the F-4 rating of the blended fuel was equivalent to that obtained with the 8- reference fuel plus 1.0 ml. of TEL per gallon of fuel. On the other hand, when 1.0% of plumbous naphthenate (wherein the valence of the lead is +2) was added to an S-reference fuel having an octane number of 100, there was no increase in the F-4 rating.

The thallous compounds of this invention are that the thallium compounds of this invention ineffective to improve the antiknock value or the Previous results showed that a metal oroctane number under lean fuel-air mixture conditions when used within the amounts specified hereinbelow. However, the thallous compounds of this invention are highly eflective as additives for spark ignition engine fuels operating at rich mixture conditions; i. e., a fuel-air mixture rich in fuel. It is a desire of this invention that these thallous compounds be used in amounts such that 0.0008% to 0.013% of monoelectrovalent thallium, based on the total fuel, is present in the prepared spark ignition engine fuel.

The following examples show the methods used in preparing some of the organo monoelectrovalent thallium compounds.

EXAMPLE I.PREPARATION OF THALLOU ETHYLA'I'E 70 grams of thallium shavings were placed in 500 ml. of absolute ethanol. This mix was heated at reflux temperatures for 6 days, .while at the same time air was bubbled through the heated mix. The alcohol was kept at constant volume by adding fresh alcohol to replace that which evaporated. The final alcohol solution of thallous ethylate had a thallium content of 0.0483 gram of thallium metal per ml. of solution. This solution was used further in the preparation of additional thallium compounds.

EXAMPLE II.-PREPARATION OF THALLOUS OLEATE 7.82 ml. of thallous ethylate solution of Example I was mixed with 0.522 gram of oleic acid to form thallous oleate.

EXAMPLE III.-PREPARATION 0F THALLIUM CETYL PHENATE 7.82 ml. of the thallous ethylate solution of Example I was mixed with 0.581 gram of cetyl phenol to form thallous cetyl phenate.

EXANHPLE IV.-PREPARATION OF THALLOUS HEPTADECYLATE 8.2 ml. of an alcohol solution of thallous ethylate containing 0.055 gram of thallium metal per ml. was reacted with 5.0 ml. of 3,9-diethyltridecanol-6. The resulting solution was blown with nitrogen for 1 hour to remove the alcohol, thus leaving a solution of thallous heptadecylate in 3,9-diethyltridecano1-6.

EXAMPLE V.PREPARATION 0F THALLOUS NAPHTHENATE A solution of naphthenic acid in 50% ethyl alcohol was neutralized with 10% caustic. this alcohol solution was being stirred rapidly, a solution of thallous acetate was added dropwise. Equivalent quantities of naphthenic acid and thallous acetate were used. At the completion of the reaction, the soap was extracted with petroleum ether and the solvent removed by blowing with nitrogen at 200 F. The thallous naphthenate had the following properties:

Properties Found Calculated Tor Cent Thallium Equivalent Weight 450 Pour Point (micro) 45 F- Solubility in Petroleum Ether.... l0%- Appearance ViscuousL1quid..

The following Table I presents data showing that thallous compounds (e. g., thallous naphthenate) are ineflective within the concentrations pertinent to this invention when the fuels While I 6 are used in spark ignition engines operating at lean fuel-air ratio.

Table I Concentrations F-l Rating F2 Rating of Monnclectrovalent Thullium Grams/ ml. Octane Octane No. Octane Octane No.

of fuel No. Improvement No. Improvement ance numbers obtained by adding incremental amounts of thallous naphthenate to an S- reference fuel. As defined hereinabove, S-reference fuel is iso-octane (2,2,4-trimethyl pentane) which has a performance number of 100.

Table I I Concentration Increase in of Monoelectro- Performance P valent Thal- Number per er & lium Grams/ Increment of 100 ml. of fuel Thallium The following Table III shows the effect in performance number obtained by (1) TEL and (2) the combined effect of a monoelectrovalent thallium compound (thallous naphthenate) and tetraethyl lead. The base fuel used was S- reference fuel.

Table III Concentration of Load Concentration P 0! Monoelectrovalent Thal- Expressed as Expressed as 2" lium (Grams/ Grams or ml. of TEL 3 100 ml. of fuel Lead per 100 per gal. of

ml. of fuel fuel As shown in Table IV, the monoelectrovalent thallium, expressed in grams of thallium per 100 m1. of fuel, is more effective than lead from TEL in improving the performance number of a fuel. The data in Table IV shown that 0.0103 gram of thallium (from thallous naphthenate) per 100 ml. of base fuel will raise the performance number of a base fuel from 100 to 126; whereas, 0.0281 gram of lead (from TEL) per 100 ml.

. of fuel are necessary to raise the periormancc 7 number of a base fuel from 100 to 126. An additional 0.0069 gram of thallium raised the performance number from 126 to 138, whereas an additional 0.0282 gram of lead was required to raise the performance number from 126 to 138. Thus, it took approximately two times more lead than thallium to raise the performance number of a fuel from 126 to 138. Similarly, in raising the performance number of a fuelfrom 153 to 161, it took approximately 10 times more lead than thallium. Thus, each incremental amount of monoelectrovalent thallium is approximately 4 to 10 times as effective as the lead from tetraethyl lead. The base fuel was S-reference fuel The following examples further show the effectiveness of organo monoelectrovalent thallium compounds for improving the F-4 rating of S- reference fuel.

EXAMPLE VI S-reference fuel was blended with the thallous oleate of above Example II so that the thallium content of the blended fuel was 0.01%. The F-4 rating of the blended fuel was .122 performance numbers which was an increase of 22 performance numbers over that of the base fuel.

EXAMPLE VII S-reference fuel was blended with the thallous cetyl phenate of above Example III so that the blended fuel contained 0.01% thallium. The blended fuel had an F4 rating of 116, an increase of 16 performance numbers over that of the base fuel.

EXAIVLPLE VIII S-reference fuel was blended with the thallous heptadecylate of about Example IV so that the thallium content of the blended fuel was 0.01%. The F-4 rating of the blended fuel was 104 performance numbers, which was an increase of 4 performance numbers over that of the base fuel.

The following Table V further shows the effectiveness of organo monoelectrovalent thallium compounds in improving the F-4 rating of a spark ignition engine fuel. S-reference fuel was the base fuel.

Table V Per Cent F-4 Rating Thallium Perform- Increase in Thallous Compound in ance N o. of Perform- Blended Blended ance No.

Fuel Fuel Thallous Oleate of Example II 0. 01 122 22 Tballous C yl Pbenate of Example III 0.01 116 16 Thallous He ptadecylate of Example I About 0.01 104 4 The above examplesand detailed descriptions of the invention set forth the preferred practices of the invention.

Not only does the presence of a monoelectrovalent thallium compound in a spark ignition engine base fuel improve the rich mixture rating of the base fuel, but the'cylinder deposits in the spark ignition engine are less when the monoelectrovalent thallium compound is used. The figure illustrates the effectiveness of a monoelectrovalent thallium compound (e. g., thallous naphthenate) in reducing the weight of piston deposits of the spark ignition engine base fuel. The tests were run over a period of hours at a rich mixture fuel-air ratio of 0.10. The figure shows the piston deposit obtained as a function of performance number. The S-reference fuel produced in the engine a piston deposit weighing 0.34 gram. When 2.0 ml. of tetraethyl lead was added to a gallon of S fuel, the blended spark ignition engine fuel was rated at a performance number of 138 and the resulting piston deposit weighed about 2.0 grams. When 6.0 ml. of tetraethyl lead was added per gallon of S fuel the per- 1. An aviation fuel consisting essentially of a gasoline boiling from about F. to about 400 F. and having a performance number of at least 100 and a small amount of a monoelectrovalent thallium salt of an organic acid sufficient to substantially improve the rich-mixture rating of said fuel but insufhcient to substantially increase the lean-mixture rating of the fuel, said small amount being such that the thallium content of the fuel is in the range from about 0.00085 to 0.013 per cent by weight.

' 2. The improved spark ignition engine fuel of claim 1 in which the organo monoelectrovalent thallium compound is thallous naphthenate.

3. The improved spark ignition engine fuel of claim 1 in which the organo monoelectrovalent thallium compound is thallous oleate.

4. The improved spark ignition engine fuel of claim 1 in which the organo monoelectrovalent thallium compound is thallous heptadecylate.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Egerton July 22, 1930 Number 1,771,169 

1. AN AVIATION FUEL CONSISTING ESSENTIALLY OF A GASOLINE BOILING FROM ABOUT 100* F. TO ABOUT 400* F. AND HAVING A PERFORMANCE NUMBER OF AT LEAST 100 AND A SMALL AMOUNT OF A MONOELECTROVALENT THALLIUM SALT OF AN AOGANIC ACID SUFFICIENT TO SUBSTANTIALLY IMPROVE THE RICH-MIXTURE RATING OF SAID FUEL BUT INSUFFICIENT TO SUBSTANTIALLY INCREASE THE LEAN-MIXTURE RATING OF THE FUEL, SAID SMALL AMOUNT BEING SUCH THAT THE THALLIUM CONTENT OF THE FUEL IS IN THE RANGE FROM ABOUT 0.00085 TO 0.013 PER CENT BY WEIGHT. 